If you're looking at the Mega stripped upper, you can get them for A LOT less at Rainier Arms and get free shipping on orders over $50. If you're looking at a complete upper, I don't know exactly what parts they're using.
I wanted a Mega upper w/ the Mega billet CH but Rainier was out of stock. Ordered the CH-less upper from Rainier Arms and the CH from Coleman-Tyler aka AR15web.com. My first transaction with them.
The transaction went smoothly. Good communication, prompt shipment. Paid over $28 (after shipping) for what would have been a $20 upgrade (free shipping)at Rainier had they been available.
One transaction isn't much to go on, but it's better than nothing.